Process of extracting copper from a sulfate solution.



No.51: vrcron nrnmnrrn, or GHRISTIANSAND, NORWAY.

YROCESS QF EXTRACTIKG COPPER FROM A SULFATE SOLUTION,

No Drawing. I

To all whom it may] concern: Be it known. that' I, NOAK V'roron Hym-NETTE, a" citizen of-the United States of America, residing atChristiansand, S., Norway, have invented certain new and useful Improvments in Processes of Extracting Copper from a Sulfate Solution; and Ido hereby such as will enableiothers skilled in the art 1 to. which itappertains to make and use the same. i The present'invention relates toa process of extracting copper from a sulfate solution which isobtainedby leaching an initial material previously roasted. In processes of thiskindsaid roasting hashitherto been effected only for the purpose ofremoving especially sulfur, so as to obtain'a leaching materialcontaining copper in the form of oxid which is dissolved by the sulfuricacid contained in the electrolyte. Generally the method of Working is sothat the ,ore is divided orground respectively into a fine powder andthen heated in a roasting fur-' v nace until. no more sulfur isoxidized.

Thereby sulfurous acid is evolved and copper oxid formed. The roasting,however,

on account of the partially occurring sintering is never quite completefor which reason undesired impurities such as iron together with copperwill be dissolved at the leaching which takes place afterwardconsiderable quantities of copper on the other hand remainingundissolved. These drawbacks are obviated according to the presentinvention by mixing the material to be roasted with sulfate of sodium.Therebya much more complete. roasting is attained, the copper containedin the roasting product being for the greatest part present as sulfateof copper.

although all the iron salt has been decomposed. T hisprocess isparticularly advantageous if other valuable metals are to be extractedfrom the ore together with the copper. Not only copper butzinc andnickel as well form with the sulfate ofsodium double salts whichdecomposes only at temexpensive were it not that it can be used over andover again as is the case according to the present invention. It; istherefore Specification of Letters Patent.

declare the following to be a full, I clear, and exact description oftheinvention, 10

onlynecessary to compensate the small mechanical losses occurring byaddition of new quantities of sodium salt. 1

An addition of sodium sulfate to the sulfidic copper ores to beroastedhas already previouslybeen rop'osed by applicant in, a

known process 0 concentration according to Patented May 25, 1915.

Application filed March 6, 1912. Serial No. 682,077.

which the ore is to be subjected-first to an I oxidizing and'thereafterto a reducing roastmg process in. order to obtain the metalcontainingparticles of the ore in a state to be readily deposited so that they maybe readily separated from the gangue by known processes of concentrationand thereby become fit for use in a subsequent smelting process. .Theobject of the present invention, however, is not to obtain a mechanicalconcentration of the roasting material, but to make the "ore suitablevfor treatment in wetway with electrolytic separation of the copper, andby experiments it has been ascertained that in the case ofiron-containing materials that have been roasted with sulfate of sodium,much less iron is dissolved with the copper, which is of greatimportance for the-subsequentelectrolytic separation of the copper. I y

The roasting as ordinarily carried out results in the formation of somekernels, which mainly consist of copper sulfids and in the followingleaching with ferric salts it is impossible to dissolve all of thesehard kernels; Applicant has found that if a small quantity of somealkali salt is added to the ore before roasting that this materiallyhelps to prevent the formation of such hard insoluble kernels. Anaddition of 2 to 5% seems to be all' that is necessary. It seems that itis immaterial what salt is added as most salt will be converted intosulfate by the reactions taking place in the furnace.

Said sulfate is united with copper sulfate to.

treatment. The solution thus obtained is" thereupon electrolyzed in awell-known manner with the use of indissoluble anodes whereby the copperis separated and free sulfuric acid is formed.

The resulting solution containing sul- .ties of the roasting product. Ifthis leaching andelectrolyzing "process; is repeated several times, thesolutionwill contain'such large quantities ofsulfate of 'sodium andother salts that it will be impossible to again use the solution forleaching purposes. This is the case when the solution'has a content ofabout 450 gr. sulfate of sodium and more per liter.- The solution mayalso contain 80 gr. of nickel or ironirespectively and up to 150 gr. ofzinc. This so ution is now used instead of new quantities of sulfate ofI sodium as an addition to' the ore to be treated in the roastingfurnace. The entire quantity of iron salts contained in the solution isthen decomposed during the roasting operation but the sulfates of othermetals such as zinc and nickel are not decomposed and are thereforereturned to the" solution at the following leaching. These metals havetherefore to be removed from the solution either by electrolysis orbyprecipitation with soda or lime. The ironand the free acid of thesolutionadded to the initial material is of great influence in makingthe.

roasting'mo're complete. 7 The iron is present in the solution as ferricsulfate and has therefore a dissolving effect on the sulfid of copper orthe sulfid of zinc or nickel respectively which isfstill present in theore on account of the incomplete roasting. The material roasted withsodium sulfate has proved to contain saidsulfids in such a mechanicalcondition that they will be far more 7 completely dissolved by theelectrolyte than if roasting without the addition of sodium sulfate. 1

It is evident that complete removal of the copper before returningtheelectrolyte to the roastingfurnace is not necessary because theremaining copper is not lost. -In

same cases it will ,be of advantage to leach with water before leachingwith the electrolyte. For the solutionthus obtained is free from ironand if it is electrolyzed until free from copper,the remaining metalscan be precipitated free from iron and copper. tesides this advantage areduction of power consumption in the electrolysis of the copper isobtained if the solution is frc'e'fi'om iron. It istherefore in somecases of great adores, which consists in vantage to leach with waterfirst and with.

acid afterward.

The small losses of sodium sulfateoccurring during the repeatedleachingmay suitably be compensated ..by adding sodium chlorid which is thendecomposed in the sulfate being ores, which consists in adding sodiumsulfate thereto according to the content of furic acid and considerableferric sulfate is then again used for leaching fresh quanti-- copperinthe ores, roasting the. ore and sulfate, thereby uniting said-sulfatewith P copper sulfate to form .an easily fusible compound for readilydissolving sulfids,

acid,' thereby simultaneously dissolvingsaid formed 'during' theroasting, and electrolyzleaching the product with dilute sulfu'ricEadded sodium sulfate with the sulfates ing the solutionobtained-to-separate the copper andrform free'sulfu'ric acid,

2. The process'of treating sulfid copper 1 ores, which consists in.adding sodiumsulfate thereto according "to, the content of copper in theores,.roasting the ore and sulfate, leaching-the productwithdilute-sulfuric acid thereby simultaneously dissolving saidaddedsodium sulfate with the sulfates formed during the roasting, and electhecopper and form free sulfuric acid and '95 'trolyzing the solutionobtained to separate to convert the ferrous sulfate into ferric sulfate,using the resultingelectrolyte containing the ferric sulfate andliberated sulfuric acid for leaching the roasted ore and sulfate'ofsodium for producing an electrolyte richer in copper and other metals. 73. The process of treating sl'ilfidjcopper addingsodium sulfate thereto,leaching the roasting the ore and sulfate, 1 product with dilutesulfuric acid thereby simultaneously dissolving. saidadded sodiumsulfate with the sulfates formed during the .roasting, and electrolyzingthe solution obtained to separate the copper and form free sulfuric acidand to convert the ferrous sulfate intoferric sul:

fate, repeatedly using the resulting electro-' has a high conroasted oreand sodium sulfateafter elechas a high coIitent of sodium sulfateandthen usingthe so lution witliraw ore, and roasting the same trolysisuntil the electrolysis trolysis until the electrolyte toeliminate"increasing quantities of iron in the solution while mamta'imng thecontent of other valuable metals.

4. The process of treating sulfid copper ores containing'iron which havebeen roasted with an alkali metal salt,'the step which compriseselectrolyzing a leaching solution from said ores to remove the copperand convert the ferrous sulfate content into ferric sulfate whilemaintaining the content of alkali metal sulfate and remixing theelectrolyte when it attains a high content of sodium sulfate, with rawore, and roasting the mixture.

5. The process of treating sulfid ores containing copper and othervalues and iron, which comprises roasting the ore in the presence of asmall percentage of sodium sulfate, thereby uniting said sulfate withthe sulfate of copper formed by the roasting to form an easily fusiblecompound, producing a sulfate solution from the roasted product,-removing the copper therefrom while converting the iron from the ferrous'to the ferric state and maintaining sodium sulfate in solution, usingthe resultin solution as a leaching solution when permissible, andreturning the solution when its sodium sulfate content has largelyincreased to the furnace with raw ore for roasting.

In testimony that I claim the foregoing as my invention, I have signedmy name in presence of two subscribing witnesses.

N OAK VICTOR HYBINETTE.

Witnesses: A

V MARTIN GULLORMSUN,

NANA SOHIANDER.

